1. Field of the Invention
The present invention relates generally to disk drives, and in particular to a method of operating a disk drive with a slider at loading and unloading fly heights greater than an operational fly height.
2. Description of the Prior Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes the disk drive base, a cover, at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA).
The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base. The spindle motor hub has an outer hub flange that supports a lowermost one of the disks. Additional disks may be stacked and separated with annular disk spacers that are disposed about the spindle motor hub. The head stack assembly has an actuator assembly including at least one air bearing slider, typically several, for reading and writing data from and to the disk. Each air bearing slider includes a magnetic transducer. An example of a slider is disclosed in U.S. Pat. No. 5,777,825 (incorporated herein by reference) that describes a slider where a center pad disposed at a trailing side contains a transducer. The printed circuit hoard assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached sliders are moved relative to tracks disposed upon the disk.
The head stack assembly includes the actuator assembly, at least one head gimbal assembly (HGA), and a flex circuit cable assembly that are attached to the actuator assembly. A conventional “rotary” or “swing-type” actuator assembly typically comprises an actuator body, a pivot bearing cartridge, a coil portion that extends from one side of the actuator body to interact with one or more permanent magnets to form a voice coil motor, and one or more actuator arms that extend from an opposite side of the actuator body. The actuator body includes a bore and the pivot bearing cartridge engaged within the bore for allowing the actuator body to rotate between limited positions. At least one head gimbal assembly is distally attached to each of the actuator arms. A head gimbal assembly includes an air bearing slider that is attached to a suspension with a gimbal. The suspension resiliently supports the slider above the tracks of the disk during operation of the disk drive facilitating the slider to “fly” above the disk. The head gimbal assemblies and the flex circuit cable assembly are attached to the actuator assembly. The actuator assembly is controllably rotated so as to move the sliders relative to the disks for reading and writing operations with respect to the tracks contained on the disks.
A typical slider design includes leading and trailing sides. A center pad that includes an air bearing surface is disposed adjacent the trailing edge. A transducer or head is embedded within the center pad. At least one additional air bearing surface disposed upon a pad is provided adjacent the leading side. In this regard, a single air bearing surface may be provided which extends the width of the slider. Alternatively, a pair of air bearing surfaces may be provided at opposite lateral sides of the slider adjacent the leading edge. In addition, a depressed region or cavity is centrally disposed between the center pad and the leading side air bearing surfaces. Furthermore, lateral pad or side rails may be disposed laterally with respect to the slider for providing aerodynamic stability, especially with respect to roll stability.
When the disk drive is not performing disk reading or writing operations, the head stack assembly is configured to pivot such that the sliders are positioned or parked at a loading/unloading ramp overlying a portion of non-data regions, such as at the ID or OD of the disks. An example of a slider is disclosed in U.S. Pat. No. 6,344,950 (incorporated herein by reference) that describes a ramp for performing slider loading and loading operations at the OD of a disk. The loading/unloading ramp supports the sliders so as to prevent undesirable contact between the sliders and the disks. When operating the disk drive, the head stack assembly is pivoted such that the sliders are moved toward the disk along the ramp with the disks rotating at an operational speed of the disk drive. The sliders become in contact with an air stream resulting from the rotating disks. The sliders are considered loaded upon being aerodynamically supported. The height at which the sliders are loaded is the loading fly height. The sliders have a defined operational fly height that is equal to the loading fly height.
When the disk drive has concluded performing disk reading or writing operations, the head stack assembly is again pivoted in a reverse direction so as to park the sliders at the loading/unloading ramp. When the disk drive in not reading or writing from and to the disk, the head stack assembly is configured to pivot the actuator assembly such that loading/unloading ramp supports the sliders. The height the sliders start to become supported by the loading/unloading ramp is the unloading fly height. This is usually the same as the loading fly height.
In order to increase the amount of data recorded upon a given disk, specifications for increasing areal density continue to increase. As a result, it is desirable to fly the slider at lower and lower heights above the tracks of the disks. However, lower fly heights increase the susceptibility of the slider coming into physical contact with the disk during operation. Such contact may result in damage to the slider, including the transducer therein, as well as the disk and the data associated with the tracks. During loading and unloading operations, the sliders may be subject to a variety of forces that may result in the sliders coming into contact with the disk. Accordingly, there is a need in the art for an improved method of operating a disk drive in comparison to the prior art.